Spatial reuse is a factor in reliable communication between multiple radios attempting to operate on a limited spectrum. Each transmitter's waveform maintains a specific transmission range on a specific frequency. This transmission range may interfere with other devices attempting to transmit and receive on or near the same frequency. Waveform interference-to-communication range ratio (I/C) has a direct effect on the ability of a network to reuse spatial resources (spatial reuse). With uncontrolled network slot allocations, spatial reuse is nonexistent.
Most wirelessly networked systems are designed with an I/C to permit reuse after two routing hops, where a hop is defined as the maximum range a transmission can be correctly received in the absence of self-interference. Beyond two hops, since the received signal power is lower than the sensitivity of the receiver, no interference is present. In contrast, when the I/C is greater than two, self-interference beyond two hops can prevent the acquisition of intended packets or cause the receiver to attempt to demodulate unintended packets. In order to maintain an acceptable packet error rate the spatial reuse must be decreased even though this also reduces throughput.
For I/C>two (certain networking waveform Signal in Space (SiS) modes), two-hop reuse can result in interference when Time Divisional Multiple Access (TDMA) slots are reassigned. Within the same network, a three-hop reuse can eliminate interference yet may result in wasted resources when no two-hop interference is present.
One limitation of traditional wireless networks (such as 802.11) may include an inability to adapt to a variety of densities and users associated with the change in density.
In mobile TDMA radio systems, the I/C also limits spatial reuse of slot allocations. In particular, the design and strength of the preamble is critical as it determines whether the packet is initially acquired and how far a transmission can capture or interfere with a receiver.
In addition, the particular receiver acquisition threshold is also critical in determining the I/C. The robustness of the preamble acquisition plays a large part in the performance of a given Signal-in-Space (SiS) modulation scheme. A stronger preamble acquisition can result in a lower packet error rate at the expense of increasing the range of interference. Extra strong preamble acquisitions may be especially frequent within some Orthogonal Frequency Division Multiplexing (OFDM) SiSs, where interfering transmitters must be at least 3 hops apart to avoid self-interference. A weaker preamble acquisition can result in less interference and thus allow increased spatial reuse, thereby increasing network throughput.
However, the challenge remains to maintain a single network in possession of both qualities of lower packet error rate resulting from a strong preamble acquisition and increased spatial reuse and network throughput of the receivers with a higher preamble acquisition threshold.